Various membrane processes may generally be applied for water treatment or industrial treatment applications. The cost effectiveness of these processes may vary depending on the specific application(s), site considerations, such as energy availability, capital costs, competitive processes and the combination of the membrane properties (such as flux, separation characteristics, performance stability, and fouling resistance as well as the ability to be cleaned when fouled). For water treatment and desalination applications, for example, to-date commonly used membranes are reverse osmosis (RO) and/or nanofiltration membranes (NF) membranes based on polyamide composites. These membranes may generally be considered to have high flux and rejection characteristics, even though from the stability and chemical resistance point there is still a need for improvement. Other NF and RO membranes, such as polysulfonated polyvinyl alcohol and sulfonated engineering plastics membranes, may generally be considered to have better chemical resistance but suffer from flux/selectivity characteristics worse than the polyamide composites membranes. It appears however that for many water applications flux and rejection may be considerably important. Therefore the development and manufacture of membranes having the flux/selectivity/rejection properties similar to (or better than) that of the polyamide membranes but with a chemical stability similar to (or better than) the chemical stability of sulfonated polyether sulfones is highly important and may considerably lower the cost of water treatment.
Existing membranes, such as composite membranes and more specifically, thin film composite membranes, suffer from many disadvantages. For example, coating of a support layer with a discriminating layer may result in variations of thickness of coating material. In areas where no coating is present or where the coating is below a certain thickness the membrane may be exceedingly porous and therefore may not have sufficient separation capability. Where the coating exceeds the desired thickness, the flux may be affected. In membranes where the discriminating layer is prepared separately, the discriminating layer may at least partially separate from the support layer.
Electrochemically initiated polymerization has been applied to deposit polymers upon a porous support, such as a membrane layer, to form composite membranes for gas separation. U.S. Pat. No. 5,198,112, which is herein incorporated by reference in its entirety, relates to ultra-thin composite membrane. U.S. Pat. No. 5,198,112 does not describe RO and/or NF membranes nor does it describe electrochemically initiated polymerization on an organic porous support.
There is thus a need in the art for improved and cost effective composite membranes that may be applied, for example, for liquid containing media such as water treatment applications.